In recent years, automotive vehicles often use an electromagnetic suspension system instead of using a hydraulic damper of a hydraulically-operated active suspension system that uses a viscous resistance of oil. One such electromagnetic suspension system has been disclosed in Japanese Patent Provisional Publication No. 7-149130 (hereinafter is referred to as “JP7-149130”). In the electric motor type suspension system disclosed in JP7-149130, a motor of the electromagnetic suspension system acts to produce a reaction torque based on a motor rotation angle, a vibration dampening torque based on a motor angular velocity, and a vehicle-body-inertia compensating torque based on a motor angular acceleration and needed to compensate for inertia force exerting on the vehicle body due to acceleration/deceleration and turning behavior of the vehicle. Actually, within an electronic suspension control system for the electromagnetic suspension system of JP7-149130, of these torques produced by the electric motor, the inertia-force compensating torque is arithmetically calculated or estimated based on a motor angular acceleration, corresponding to vertical inertia force exerted on the vehicle during driving. Such an electromagnetically-operated suspension system as disclosed in JP7-149130 can quickly variably control a suspension characteristic by controlling the magnitude of exciting current applied to the electromagnet of the electric motor. Generally, the responsiveness of the electromagnetically-operated suspension system is superior to that of the hydraulically-operated active suspension system.